Born of Cree ancestry in Sandy Lake, Ontario, Joshim began painting as a teenager under the guidance of his Ojibwa brother-in-law Norval Morrisseau and fellow Cree artist Carl Ray. Josh joined Morrisseau and Carl Ray in the late 60s when they held demonstration classes in schools across Ontario. He took part in a group show in North Bay in 1969

In 1973 with the help of his brothers Goyce and Henry and his father, David, he established the Triple K Cooperative, a silk screening operation in Red Lake, Ontario which operated for ten years. It was modelled after a company Daphne Odjig had set up in 1970 - Indian Prints of Canada Ltd.

In the 1970s and 1980s, he took part in a number of exhibitions throughout Ontario and other venues in Canada, as well as in a group show, Woodland Indian Art Exhibition, at Canada House in London, England and Lahr, Germany. He was also featured in a major exhibition at Toronto's Aggregation Gallery in 1977.

Josh drowned in a lake in northwestern Ontario in 1993 while on a rescue mission. His work is in private and public collections in Canada and abroad including Simon Fraser University Art Center, the McMichael Canadian Collection and the Royal Ontario Museum and others.